Projectile



Feb. 11, 1964 G. H. CUSTARD 3,120,809

PROJECTILE Filed Jan. 11, 1962 INVEN TOR. GEORGE H. CUSTARD ATTORNEYS:

United States Patent 3,120,809 7' PROJECTLLE George H. Custard, Denver, Colo., assignor, by mesne assignments, to the United States of America as represented by the Secretary of the Army Filed Jan. 11, 1962, Ser. No. 166,464 6 Claims. (Cl. 102-66) This invention relates to a high explosive projectile and has for an object to provide a high explosive incendiary projectile which is equivalent in explosive and incendiary character to a current standard explosive known as MOX- 2B and superior thereto in resistance to cook-oil. This last term refers to the danger of a premature explosion by heat transfer through the cartridge case walls. The MOX-2B is a high explosive incendiary having the following composition in parts by weight: aluminum powder 52%, ammonium perchlorate 35%, cyclotrimethylene trinitramine wax 6%, calcium stearate 2%, graphite 1%, and trinitrotoluol 4%.

In a machine gun it is known that after use the temperature of the gun becomes dangerously high with the result that an explosion may be prematurely started by conduction of heat through the cartridge case walls from higher temperature walls of the firing chamber when a cartridge is held in the ready to fire position. One practice with machine gunners has been to use up more cartridges than may be needed after prolonged use in order to leave no cartridge in the gun ready to fire. After prolonged use the gun may reach a temperature of around 1000 F. Ordinary high explosive incendiary projectiles have not been able to withstand high temperatures of as much as 400 F. to 500 F. contiguous to the explosive although one or two such explosives have been found to be capable of standing such temperatures under the prior art in steel bodies of projectiles.

According to the present invention a high explosive incendia-ry projectile has been provided capable of withstanding a much higher cook-01f temperature with safety of about 40% or more depending on the type of walls in contact with the explosive.

The single figure of the drawing shows a longitudinal view partly in section of a standard 20 millimeter projectile containing the present high explosive incendiary material.

The nose 10 contains the usual impact responsive primer not shown. The body walls 11 are of steel provided with the usual soft metal rotating band 12. A top-off booster charge 13 of TNB (trinitrobenzene) of about 30 grains is shown above the main body improved explosive 14 of this invention. That main charge is of about 100 grains of the following composition expressed in percent by weight: 50% aluminum in powder form having particles no smaller than of a size to be held by a. 325 mesh screen and small enough to pass through a 100 mesh screen, 18% barium nitrate Ba(NO powder, and 32% 1,3,5 (TNB) trinitrobenzene of reagent grade crystalline powder having a melting temperature of about 250 F.

In a standard steel body 20 millimeter projectile a cook-off temperature of about 700 F. was obtained with the above improved explosive which was observed to possess explosive and incendiary characteristics at least about equal to those of prior explosive incendiaries but about a 40% improvement in cook-off temperature when 3,120,809 Fatented Feb. 11, rsea compared with the closest known prior art and considerably better than other explosive incendiaries which have been in use. In a copper tube this improved explosive was found to have a cook-off temperature of about 1000 F. The powdered mixture of the present explosive hav ing the improved cook-oft temperature was loaded in increments about 25 to 50 grains into the standard 20 millimeter projectile steel body and compressed under about 30,000 pounds per square inch. The reason for the difference in cook-off temperatures of the present explosive in copper and steel containers is not known. One theory advanced for the different results is that when the barium nitrate decomposes at elevated temperature,

the oxygen released reacts more readily with copper than with steel requiring a higher temperature to increase the rate of barium nitrate breakdown to provide sufiicient oxygen to react with the TNB. The TNB is believed to have a melting temperature above that mentioned when mixed with other materials.

I claim:

1. A high explosive incendiary projectile having improved cook-oif temperature characteristic-s containing an explosive fill of metalized composition and containing about 50% by weight of aluminum powder, about 18% by weight of barium nitrate, and about 32% by weight of 1,3,5-trinitrobenzene, all in powdered form.

2. An explosive according to claim 1 in which the aluminum powder is able to pass through about a mesh screen but not through a 325 mesh screen, and the trinitrobenzene is of reagent grade having a melting point of 250 F.

3. An explosive according to claim 2 which has been loaded into the body of a 20 millimeter standard projectile under about 30,000 pounds per square inch pressure and has a cook-off temperature of about 700 F. in a steel projectile.

4. An incendiary 20 millimeter projectile containing an impact responsive means for firing a main charge, a top-off booster charge of about 30 grains of trini-trobenzene forward of a main charge of about 100 grains with the following composition expressed in percent by weight: 50% aluminum powder having particles no smaller than of a size to be held by a 325 mesh screen but small enough to be passed through a hundred mesh screen, 18 barium nitrate powder, and 32% 1,3,5t rinitrobenzene of reagent grade crystalline powder having a melting temperature of about 250 F.

5. A projectile according to claim 4 having a steel body with a cook-01f temperature of about 700 F. for the charge.

6. A projectile according to claim 4 having a copper tubular body with a cook-off temperature of 1000 F. and with at least the main charge compressed under a pressure of about 30,000 pounds per square inch.

References Cited in the file of this patent UNITED STATES PATENTS 2,669,182 Weiss Feb. 16, 1954 FOREIGN PATENTS 13,373 Great Britain 1912 16,681 Great Britain 1914 20,307 Great Britain 1914 476,263 France May 1, 1915 

1. A HIGH EXPLOSIVE INCENDIARY PROJECTILE HAVING IMPROVED COOK-OFF TEMPERATURE CHARACTERISTICS CONTAINING AN EXPLOSIVE FILL OF METALIZED COMPOSITION AND CONTAINING ABOUT 50% BY WEIGHT OF ALUMINUM POWDER, ABOUT 18% BY WEIGHT OF BARUM NITRATE, AND ABOUT 32% BY WEIGHT OF 1,3,5-TRINITROBENZENE, ALL IN POWDERED FORM. 